A vehicle ignition interlock system includes a breath analyzer, a transdermal alcohol sensor configured to be worn by the vehicle operator, and a controller operably connected to the breath analyzer, to the transdermal alcohol sensor, and to an ignition system of the vehicle. The transdermal alcohol sensor is configured to be worn by the vehicle operator, and is configured to detect alcohol through the skin of the vehicle operator. The controller is configured to override one or more periodic breath analyzer retests if alcohol is not detected through the skin of the operator by the transdermal alcohol sensor. The controller is configured to increase the frequency of periodic breath analyzer retests of the vehicle operator in response to the transdermal alcohol sensor detecting alcohol through the skin of the operator. A proximity sensor detects proximity of the transdermal alcohol sensor relative to a vehicle operator area.